1. Department of Hygiene, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan
2. Division of Bioscience, Department of Biofunctional Chemistry, Okayama University Graduate School of Natural Science and Technology, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
3. Division of Pneumoconiosis, School of Public Health, China Medical University, 92 North 2nd, Heping District, Shenyang 110001, China
4. Department of Radiation Oncology, Kawasaki Medical School, 577 Matsushima, Kurashiki 701-0192, Japan